• mutants exhibit delayed and defective fracture healing characterized by diminished cartilaginous callus formation, increased bone formation near the cortical bone on the periosteum but not in the fracture gap, and persistence of cartilage at day 21 such that bony bridging is not observed

• while total callus volume following fracture is larger in mutants at day 7 and 10 due to rapid initial growth of fibrous tissue (desmal type ossification), by day 14 and 21, the total callus volume is significantly smaller

• accumulation and persistence of fibrous tissue in the fracture gap, with increased numbers of osteoclasts

• increase in number of blood vessels in mutant fractures (in callus) compared to controls, indicating increased vascularization of the fracture tissue, however no osteogenesis results from this increased vascularization

• mutants exhibit delayed and defective fracture healing characterized by diminished cartilaginous callus formation, increased bone formation near the cortical bone on the periosteum but not in the fracture gap, and persistence of cartilage at day 21 such that bony bridging is not observed

• while total callus volume following fracture is larger in mutants at day 7 and 10 due to rapid initial growth of fibrous tissue (desmal type ossification), by day 14 and 21, the total callus volume is significantly smaller

• accumulation and persistence of fibrous tissue in the fracture gap, with increased numbers of osteoclasts

• increase in number of blood vessels in mutant fractures (in callus) compared to controls, indicating increased vascularization of the fracture tissue, however no osteogenesis results from this increased vascularization